1. Field of the Invention
The present invention relates to an apparatus for condensing and recycling liquids and, more particularly, to a method and an apparatus for increasing the uniformity of concentration of stripper in a stripper recycling system.
2. Description of Related Art
During the processing of semiconductors or flat panel displays, photoresists are required for carrying out photolithography and etching procedures to form specific circuit patterns on silicon substrates. After the etching, a stripper solution is applied to strip out redundant photoresists.
Currently, most of the exhausted strippers are collected and drained to a stripper buffer tank by collection pipes. The recycled stripper collected by the stripper buffer tank is a mixture of solvents, base and photoresist in most cases. For example, the common recycled stripper is composed of 19.3% of MEA, 77% of BDG, 3% of PR, and 0.7% of H2O. The other exhausted stripper not directly drained to the stripper buffer tank are first drawn to a stripper condenser by the exhaust system, and further become a condensed liquid composed of 50% of MEA, 23% of BDG, and 27% of H2O, and is then conducted into the stripper buffer tank. After being mixed in the stripper buffer tank, the recycled liquids and condensed liquids are purified by the recycling system to have a required concentration for reuse in normal processes.
A liquid waste disposing device is commonly mounted in the stripper recycling system. The liquid waste disposing device installed in the stripper recycling system can drain unusable liquids to another liquid waste processing system. The recycling system is preset with an exhaust amount of liquid waste according to the concentration of impurity in a previous feedstock of a recycling system so that the recycled liquids produced by the recycling system may meet the requirements of normal processes. If the concentration of impurity according to which the recycling system is preset with an exhaust amount of liquid waste is relatively less than the actual concentration of impurity of the feedstock to recycling system, i.e., the concentration of impurity of the feedstock to recycling system is relatively high, the recycled liquid obtained will not match the required qualities and can not be reused. In this situation, the exhaust amount needs to be enlarged for ensuring the recyclability of recycled liquids produced by the recycling system. Therefore, the exhaust amount of liquid waste preset in the recycling system must be based on the possible highest concentration of impurities of feedstock to the recycling system if the concentrations of impurities of the feedstock are not stable. However, such a concentration will result in too much exhaust of usable chemicals and cause a decrease of the recycling rate and results in a waste of resources.
Therefore, it is desirable to provide an improved apparatus and method for condensing and recycling strippers to mitigate and/or obviate the aforementioned problems.